So i'm pretty light on experience in both areas. I've used one mini-x (borrowed) and one backhoe (mine), both maybe 30-40hrs each. But, i have used both!
I would say the main thing you notice with the tractor backhoe is that you can pick up dirt but you have a lot harder time putting it down, as in you run out of space to dump the material you're digging up pretty quick just because you're limited to that ~180 degree swing unless you want to move the machine.
2nd thing is the reduced reach vs typical mini-x. Also reduces your options for dropping material and requires moving more often.
3rd harder to move the machine.
So you could say a tractor backhoe is like 1/3rd the digging machine that a mini-x of comparable overall size (not reach) is, but.. it could be LESS than 1/3rd the price. I got a crazy deal on my
B8200 w/subframe backhoe needing work.. but there basically ARE no crazy deals on mini-Xs because everyone wants one. Cheapest i've seen locally was like 8k needing an unknown amount of work. I'd have to get an older one the right size for like 4k, and from what i've seen it's not gonna happen because a: there aren't many out there, and b: if someone lists a mini-x of any anything whatsoever for 4k it's gonna sell in 30 seconds and i'll never see it.
So im pretty happy with what i've got because it's what im willing to afford. As a lifelong mechanic who always buys things broken for pennies on the dollar (like my backhoe) a mini-x just isn't realistic and i don't have enough of a need to spend what they're 'worth' to get one at normal prices.
What i MIGHT do, is put a full backhoe attachment (with swing, outriggers etc) on the front of my tiny skid steer. It'd sure be cheaper than buying a mini-x but would address a lot of the issues.